The 2021 CT4 is part of GM's Alpha-II platform with two turbo engines. The 2.7L turbo has shown catastrophic low-speed pre-ignition (LSPI) failures that grenade engines, while the 2.0L has been relatively reliable but isn't immune to GM's 8-speed automatic transmission quirks.
2.7L Turbo Catastrophic Engine Failure (LSPI)
Occasional · high severity
Typical onset: 15,000-60,000 mi
Symptoms: Sudden knocking or rattling under light acceleration at low RPM, Metal fragments in oil during routine changes, Check engine light with misfire codes followed by complete loss of power, Catastrophic failure can happen without warning—connecting rods through block
Fix: Full engine replacement or rebuild required. GM has extended warranty on some VINs but coverage is inconsistent. Rebuild involves all new pistons, rings, bearings, often crankshaft. 25-35 labor hours for short block swap, 40+ for complete teardown and rebuild.
Estimated cost: $8,000-15,000
8-Speed Automatic Transmission Shudder and Harsh Shifts
Common · medium severity
Typical onset: 30,000-70,000 mi
Symptoms: Shudder or vibration during light acceleration, especially 25-45 mph, Harsh 2-3 or 3-4 upshifts when cold, Delayed engagement into Drive or Reverse after sitting, Check engine light with torque converter clutch codes
Fix: Often requires torque converter replacement and valve body update. Sometimes transmission fluid flush with GM-specific fluid helps temporarily. Transmission out and R&R is 8-12 hours. Some units need complete overhaul or replacement at higher mileage.
Estimated cost: $2,800-5,500
Transmission Oil Cooler Line Leaks
Common · medium severity
Typical onset: 40,000-80,000 mi
Symptoms: Transmission fluid spots under vehicle, typically passenger side, Low transmission fluid warning on dashboard, Burnt transmission fluid smell, Cooler lines corrode or connection points crack at radiator
Fix: Replace transmission cooler lines and sometimes the entire external cooler assembly. Lines run along subframe and require partial suspension drop for access. 3-5 labor hours plus fluid refill and system purge.
Estimated cost: $600-1,200
Rear Curtain Airbag Deployment Issue (Recall)
Rare · high severity
Symptoms: No visible symptoms until deployment event, Airbag warning light may illuminate in some cases, Recall issued for potential non-deployment in side-impact crashes
Fix: Factory recall requires headliner removal and side curtain airbag replacement. Dealer-only repair, 4-6 hours. Check if your VIN has been serviced—many owners unaware of open recall status.
Estimated cost: $0 (recall covered)
Turbocharger Wastegate Rattle (2.0L)
Occasional · low severity
Typical onset: 50,000-90,000 mi
Symptoms: Rattling noise from engine bay on cold start that disappears after warm-up, Intermittent rattle during deceleration, No performance loss initially but can progress to boost control issues
Fix: Wastegate actuator arm wears and develops play. Some techs try lubricating the pivot, but proper fix is turbocharger replacement or rebuilt unit. Turbo R&R on the 2.0L is 6-8 hours due to tight engine bay and intercooler routing.
Estimated cost: $1,800-3,200
Fuel System Carbon Buildup (Direct Injection)
Common · low severity
Typical onset: 60,000-100,000 mi
Symptoms: Rough idle, especially when cold, Misfires on multiple cylinders, Loss of power during acceleration, Check engine light with lean fuel trim codes
Fix: Both engines are direct-injection only (no port injection to clean valves). Requires walnut blasting of intake valves. Intake manifold removal, 4-6 hours labor. Should be done as preventive maintenance every 60-80k miles.
Estimated cost: $500-900
Owner tips
If buying a 2.7L turbo, get pre-purchase compression test and borescope inspection—many grenaded engines had no warning
Change transmission fluid at 50k miles with GM Dexron ULV only, not generic ATF—helps prevent shudder
Use Top Tier fuel and occasional high-RPM runs to minimize carbon buildup on direct-injection engines
Check for open recalls via NHTSA—side curtain airbag recall often unrepaired on used units
The 2.0L turbo CT4 is a solid buy with proper maintenance history; avoid the 2.7L turbo unless you have documented proof of engine replacement under warranty or can afford the gamble of a $12k repair.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
Fitment notes: AGM battery required; located in trunk
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Every control module on the 2020-2026 Cadillac CT4 — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
Electric Power Steering Control Module (EPSCM)2.0 hr R&Rdealer / factory tool +0.8 hr▸ programming details
📍 Integrated into steering column assembly or steering gear
🔧 GM Techline Connect + MDI2
⚠️ Steering angle sensor calibration required; may require column removal depending on configuration
Body Control Module (BCM)1.8 hr R&Rsecurity gateway +1.2 hr▸ programming details
📍 Behind instrument panel, driver side kick panel area
🔧 GM Techline Connect + MDI2
⚠️ Controls all body functions; replacement requires extensive configuration of options and accessories
⚠️ Memory seat positions lost; customer must reprogram preferences
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
General Motors LLC (GM) is recalling certain 2019-2020 Cadillac CT6, 2020-2021 CT4, CT5, and 2020-2022 Chevrolet Camaro vehicles equipped with a 10-speed transmission. The transmission may become damaged internally and cause the wheels to lock-up.
Consequence: Wheel lock-up while driving increases the risk of a crash.
Remedy: Dealers will install transmission control module monitoring software, free of charge. Owner notification letters were mailed April 7, 2025. Owners may contact Cadillac customer service at 1-800-333-4223 or Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N242480630.
EXTERIOR LIGHTING:LIGHTING CONTROL MODULE:SOFTWARE · 22V903000
2022-12-08
General Motors, LLC (GM) is recalling certain 2020-2023 Cadillac CT4 and CT5; 2021-2023 Buick Envision; and 2022-2023 Cadillac Escalade and Escalade ESV, Chevrolet Silverado 1500, Suburban, Tahoe, GMC Sierra 1500, Yukon, and Yukon XL vehicles. The daytime running lights (DRLs) may not deactivate when the headlights are on. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 108, "Lamps, Reflective Devices, and Associated Equipment."
Consequence: DRLs that do not deactivate as intended may result in a glare, reducing visibility, and increasing the risk of a crash.
Remedy: The body control module software will be updated by a dealer, or through an over-the-air (OTA) update, free of charge. Owner notification letters were mailed January 23, 2023. Owners may contact GMC customer service at 1-888-988-7267, Chevrolet customer service at 1-800-222-1020, or Cadillac customer service at 1-800-458-8006. GM's number for this recall is N222386380. This recall expands previous recall number 22V-827.
AIR BAGS:SIDE/WINDOW:CURTAIN · 21V611000
2021-08-05
General Motors, LLC. (GM) is recalling certain 2020-2022 Cadillac CT4 and CT5 vehicles. The roof rail side-curtain air bags may not have been installed correctly, which could result in an improper air bag deployment during a crash.
Consequence: Air bags that do not deploy properly can increase the risk of injury in a crash.
Remedy: Dealers will inspect both left and right-side roof rail air bags and reinstall the air bags, as necessary, free of charge. Owner notification letters were mailed on August 30, 2021. Owners may contact Cadillac customer service at 1-800-458-8006. GM's number for this recall is N212342780.
AIR BAGS:SRS MALFUNCTION WARNING LAMP/LIGHT · 21V421000
2021-06-10
General Motors, LLC (GM) is recalling certain 2021 Buick Envision, Cadillac CT4, CT5, Escalade, Escalade ESV, Chevrolet Tahoe, Corvette, Suburban, GMC Yukon, Yukon XL vehicles. The communications gateway module incorrectly processes a loss of communication with the sensing diagnostic module (SDM), causing the air bag malfunction indicator light to inconsistently illuminate.
Consequence: The air bag malfunction indicator light may fail to warn the driver of a problem with the air bag, increasing the risk of injury.
Remedy: The communications gateway module software will be updated by a dealer, or through an over-the-air (OTA) update, free of charge. Owner notification letters were mailed on July 1, 2021. Owners may contact Buick customer service at 1-800-521-7300, Cadillac customer service at 1-800-458-8006, Chevrolet customer service at 1-800-222-1020, or GMC customer service at 1-800-462-8782. GM's number for this recall is N212338110.
Performance
Horsepower
310hp
Torque
350lb-ft
0–60 mph
5.8sec
Quarter mile
14.3sec
Top speed
143mph
Fuel economy (EPA)
City
21mpg
Highway
31mpg
Combined
25mpg
Fuel
Premium Gasoline
Capability & size
Curb weight
3,617lb
EPA class
Compact Cars
Wiper blades
Modern Cadillac sedan with asymmetrical blade configuration. Uses push-button style quick-release attachment typical of GM vehicles from this era.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2021 Cadillac CT4 2.7L Turbo I4 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.